Which of the following illnesses involves an animal-borne transmission?

Psittacosis is an illness that results from infection with the bacterium Chlamydia psittaci, which is often transmitted to humans through contact with infected birds, particularly pet parrots, pigeons, and other avian species. This zoonotic disease highlights how certain infections can be spread from animals to humans.

In contrast, the common cold and the flu are primarily transmitted from person to person through respiratory droplets, and strep throat is caused by Group A Streptococcus bacteria, which is also spread through direct contact with infected individuals or contaminated surfaces. Therefore, psittacosis is unique among the options as it specifically involves transmission from animals to humans, making it the appropriate choice.